I was considering using Yamaha's AMQ to minimize jitter on my CDs, but I would have to use a 99 minute CD-R to fit an 80-minute commercial CD and is there any reason to think they won't eventually release 90+ minute audio CDs that therefore will not be able to be burned via AMQ?

Tonearm wrote:I was considering using Yamaha's AMQ to minimize jitter on my CDs, but I would have to use a 99 minute CD-R to fit an 80-minute commercial CD and is there any reason to think they won't eventually release 90+ minute audio CDs that therefore will not be able to be burned via AMQ?

I doubt they will release commercial CD's beyond 80 minutes, since discs of such length are outside of the CD specifications, and thus not all players can play them. Which is something you need to consider for your own recording of an 80-minute disc onto a 99-minute blank with AMQ. Those 99-minute discs won't work in some players. You might want to stick with 80-minute discs and only use AMQ for sources that will fit. For longer sources, turn off AMQ and record normally.

One more thing. Although AMQ is designed to reduce jitter, there are reports that some audio drives have a hard time playing AMQ discs. Presumably this is because the linear velocity is outside of the 1x playback specification?? It appears that AMQ may improve jitter on drives that support its playback, but might also cause problems for other drives. These are just anecdotal reports I am relaying. I don't know if a rigorous investigation has been performed.

Tonearm wrote:So, 80 minute CDs weren't outside of the CD spec when they were first released?

They were outside the original specifications. But I don't expect any further changes to include 90+ media. CD's, as a technology, are quite mature now. Things have been settled down for quite some time, and further advancements will likely be confined to the SACD and DVD audio realms.

Yamaha decided to deal with this by creating a process they called Audio Master. They decided to artificially slow down the speed of burning by increasing the length of the pits and lands. Although the disc is still spinning at its 24x or 32x speed, the density of bits on the CD's goes down. The normal 1.2 m/s linear speed turns into 1.4 m/s. 74 minute discs suddenly only hold 63 minutes, and 80 minute discs now only hold 68 minutes due to the extended pit length. Although the feature sizes are increased, they're still within Red Book standards. Now the reader's laser has more room with which to sample and determine if it's actually looking at a pit or a land.

[my emphasis]

One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the land of Mordor, where the Shadows lie
-- JRRT
M.C. Escher - Reptilien

I was focusing on the part where "the normal 1.2 m/s linear speed turns into 1.4 m/s". (my emphasis ). I don't know if that is the actual cause of problems or not. Sometimes devices are tuned for the expected rather than the possible, even if the possible remains within the standard. So even if everything is within spec, the fact that it is outside of normal expectations may cause an issue. Or maybe not. I was just speculating (hence the ??). And, as I said, I was just relaying anecdotal reports, not describing the results of rigorous investigation.

Realistically, it shouldn't make any difference for a modern drive, since they are capable of reading at linear speeds far in excess of 1.2 m/s. After all, a 52x reader at speed must be reading at 62.4 m/s. But some of the reports I read were for problems playing in audio players which may not be tuned for higher speed (even if only slightly) reading and/or larger pits and lands.

My main intention was to point out that AMQ isn't unequivocally better, and while when it works it may make things better, there are also anecdotal reports that for some players it can make things worse - as in unplayable at all. It is hard to know the truth, since so many variables are involved.